Multistandard-Multiband radio base stations, i.e. the radio transmitters comprised in said type of base stations, must have tuneable or switchable radio filters in connection with an output amplifier radio stage in order to prevent impairments of radio conditions in other radio cells and/or on other radio bands. Generally, electrical filter characteristics such as mid frequency, quality factor, etc., of a tuneable filter can be adjusted by means of a number of electric actuators (generally in the form of motors) which are disposed at the antenna network for interaction with suitable filter adjusting elements, e.g. screws, chambers, lengths, etc.
In the prior art, a look-up table is provided which comprises corresponding filter tuning or adjusting values for a given radio frequency or operation point of the above-defined radio transmitter/base station.
Accordingly, for a given operating point, for instance a predefined radio frequency of the tuneable filter, said actuator means drive the tuneable filter to a predefined point of operation in accordance with values comprised in said look-up table.
This approach suffers from the inherent disadvantage that due to aging effects and variable temperature characteristics within the radio transmitter or base station the characteristics of a tuneable filter generally are not tuned in an optimised fashion.